I just upgraded www.hollenback.net from an October 2004
1.3.10 to 1.3.11rc3. the action=upgrade failed the
first time I did it because /tmp/cache didn't exist. I
manually created this file and then the upgrade worked.
I am unsure what that is about. From config.ini, it
seems that dir is used by the plugin cache.
If that dir is now always needed, the upgrade procedure
should attempt to create it if missing. If that fails,
action-upgrade should fail gracefully and tell the user
to create the directory manually.